Apparatus for centering irregular peeler logs

ABSTRACT

This invention relates to a centering apparatus for peeler logs with substantially noncircular cross sections, slight taper and some circular sweep, known to have two critical cross sections at about one sixth of the length from each end. The center points of the maximum circles in each of these two critical cross sections define, for geometrical reasons, the peeling axis of the log. Each periphery of a critical cross section of the log is determined by a number of points on the periphery. Each point is sensed by a displacement transmitter and simultaneously duplicated in a periphery duplicating unit. In each duplicated periphery the center point of the maximum circle is found. One means for finding the center point is a free floating variable diameter cylinder contracting or expanding within the duplicated periphery. Another means is a rigid free floating cylinder within the duplicated periphery, which is grasped firmly by the proportionally contracting periphery.

United States Patent 1 Nilberg June 24, 1975 I APPARATUS FOR CENTERING IRREGULAR PEELER LOGS Reinhold Hermann Nilberg, 463 Beachview Dr., North Vancouver, Canada [22] Filed: June 14, 1973 [21] Appl. No.: 369,837

[76] Inventor:

Primary Examiner-Donald R. Schran 57 ABSTRACT I This invention relates to a centering apparatus for peeler logs with substantially noncircular cross sections, slight taper and some circular sweep, known to have two critical cross sections at about one sixth of the length from each end. The center points of the maximum circles in each of these two critical cross sections define, for geometrical reasons, the peeling axis of the log, Each periphery of a critical cross section of the log is determined by a number of points on the periphery. Each point is sensed by a displacement transmitter and simultaneously duplicated in a periphery duplicating unit. In each duplicated periphery the center point of the maximum circle is found. One means for finding the center point is a free floating variable diameter cylinder contracting or expanding within the duplicated periphery. Another means is a rigid free floating cylinder within the duplicated periphery, which is grasped firmly by the proportionally contracting periphery.

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SHEET 5 Fig. J.

APPARATUS FOR CENTERING IRREGULAR PEELER LOGS Reference is made to a first or pending patent appli- 1 cation by same Applicant of Sept. 14, 1970 Ser. No. 71,698 of same title. The disclosure of this application contains subject matter described in an amendment to the first application which was rejected as new matter.

A centering apparatus is part of a lathe for rotary peeling of veneer. The log is chucked, at each end, in the lathe and the center points of the chucks determine the peeling axis.

The amount of continuous full-width veneer recovered, along the full length of the log, depends on the position of the peeling axis within the mantle ofthe log. The purpose of a centering apparatus is to find a peeling axis that gives the maximum recovery of full width veneer. The ideal peeling axis is determined by a straight cylinder, as long as the log and '-fully surrounded by the log mantle and positioned within,the mantle so that its diameter is a maximum.

If the log is tapered, so that one end is substantially larger than the other, then a centering apparatus must operate in such a manner that in addition to the maximum recovery of full width veneer, an optimum of half width veneer is recovered at the larger end of the log.

The only known method for centering of logs with non-circular cross sections is the optical centering method. This method applies two fixed projectors, facing each other on a common axis called the datum axis, at a distance exceeding the length of the log. The datum axis is parallel to the lathe axis, it is generally in the same horizontal plane with the lathe axis and it has a fixed distance from the lathe axis. The log is positioned between the projectors on two supports. Each projector puts on the nearest end face of the log a series of concentric circles. Each log support is shifted by the operator horizontally and vertically so that within the periphery of the end face appears the largest possible circle. The log is centered and transferred to the lathe.

The advantage of the optical method is that an experienced operator easily puts the maximum circle onto an end face with a noncircular periphery. The log can be tapered to any degree but must be straight. Both full width and half width veneer are correctly recovered. The disadvantages of the method are that it isnotapplicable to swept or curved logs and the centering of straight logs is good only when operator has sufficient time for centering. The time required is available only on large diameter logs, because of the long peeling time. Small diameter logs have a very short peeling time and are therefore centered automatically.

Automatic centering consists essentially of finding the center points of the maximum circles in the periphcries of two critical crosssections of the log. One cross section is positioned at about one sixth of the log length from one end and the other is at the same distance from the other end. These two center points determine adequately the peeling axis for logs with circular sweep and slight taper. The above mentioned cross sections must have a point of symmetry for correct conventional; centering. There is no centering apparatus available for irregular or nonsymmetric cross sections.

Nonsymmetric cross sections, such as egg shaped cross sections and cross sections with knots, introduce incorrect centering. It has been estimated that the losses from incorrect centering of logs with irregular cross sections, sweep and taper, exceed 5 percent of the total amount of continuous full width veneer recovered. The best quality of veneer'is obtained early and correct geometrical centering would increase the amount of best quality veneer in excess of 10 percent of the total amount of best quality veneer recovered.

From tests made on an experimental set up, I found that a straight cylinder, continuously expanding diametrically within an irregular periphery, puts itself automatically into the position of the maximum diameter. The basic idea of the new method for automatic centering of logs with nonsymmetric cross sections consists essentially of theduplication of the critical cross sections and the expansion of a straight cylinder within the duplicated periphery of each cross section.

Further tests showed that a straight rigid cylinder, of such constant diameter that it can float freely withi-na duplicated periphery, shifts itself automatically into the position of the maximum circle while the duplicated periphery is contracted proportionally till the contracting periphery holds firmly the cylinder.

Assuming that a log is positioned before a veneer lathe on two supports, each movable horizontally and vertically. The periphery of each critical cross section can be represented by a number of points on the periphery with chords in between. The higher the number of points the better the periphery is defined for duplication, especially when knots are present on the periphery.

The position of each chosen point on one periphery of the log mantle can be determined by conventional linear displacement transmitters. All transmitters for one periphery are preferably in a plane, determined by the periphery, so that the axes of the racks of these transmitters cut the datum axis in one common point. The position of the tip of the rack of each linear displacement transmitter, in one periphery, can be duplicated by a corresponding linear displacement receiver in the duplicating unit and the gaps between the tips of the racks can be closed with a steel wire under tension, running freely through the tips and representing chords of the periphery.

The mantle of a cylinder can be represented by straight lines parallel to the axis and at the distance of the cylinder radius. The higher the number of. these straight lines, the better the mantleof the cylinder is represented. If all linesrepresenting the mantle of the cylinder are shifted in radial direction at the same rate, so that all lines stay parallel to the axis and equidistant from the axis, then the cylinder is expanding or contracting uniformly.

In this centering apparatus the straight line sections, representing the mantle of the cylinder, are rods attached at each end to a system of umbrella type spokes, so that the common shaft of both umbrella systems is also the axis of the variable diameter cylinder. Shifting of 'both umbrella systems, at the same rate in same direction along the common shaft, expands or contracts the rodcylinder uniformly. When'this cylinder is allowed to expand itself freely within the duplicated periphery of acritical cross section, then in the final static position the cylinder has the maximum possible diameter in this periphery. In practice the variable diameter cylinder'is contracted from its largest, diameter, as determined by the fully retracted displacement receivers, into its final static position and it was found that this contraction has no adverse effect on the final static position.

The position of the cylinder within the duplicated periphery is sensed by a cylinder axis sensing unit and then the log is shifted by the supports so that the center point of the maximum circle in each critical cross section is on the datum axis of the supports. The log is centered and ready for transfer to the lathe. Sensing of the peripheries, duplication of peripheries and sensing of the cylinder axis are preferably simultaneous operations. The cylinder axis sensing unit shifts the supports of the log after the racks for sensing the peripheries on the log proper, are retracted.

In drawings which illustrate the embodiments of the invention:

FIG. 1 is a side view of a periphery sensing unit and a side view of a servo unit for shifting one log support. FIG. 2 is a sectional view of a periphery duplicating unit for one critical cross section.

7 unit.

FIG. is a sectional view of a periphery duplicating unit with a constant diameter cylinder.

FIG. 1 shows one ring 7, 8 for one critical cross section and one log support 3 in a seperate cross section. The periphery of this critical cross section is represented by 16 points and each point is sensed by one linear displacement transmitter 9 mounted on ring 7, 8 consisting of a lower half 7 and an upper half 8. For the purpose of sensing, the upper half 8 is lowered on the corresponding lower half 7, after log 2 is rolled along rails l on supports 3.

Linear displacement transmitter 9, FIG. 1, is air pressure operated, in such manner that a positive pressure pushes rack 12 with rack tip 13 on the log and a negative pressure retracts the rack. Rack 12 is operating an electrical potentiometer 14, so that the voltage output of the potentiometer is proportional to the linear displacement of the rack tip 13. This voltage operates the servo mechanism 22, 23 in FIG. 2 of the corresponding displacement receiver 21 mounted on ring of the duplicating unit. When the potentiometer voltage from 23 is exactly the same as from 14 then tip 24 of receiver rack 21 has travelled the same distance as tip 13 of transmitter 12. The log mantle sensing tip 13 of rack 12 is a roller of the same diameter as the roller 24 in FIG. 2, if the duplication is one to one. The periphery duplicating unit, as shown by FIG. 2 consists of two periphery duplicating rings 20, each duplicating same periphery. This double duplication of one periphery ensures that the cylinder axis is perpendicular to the plane of the duplicated periphery. Between duplicating rings 20 FIG. 2, there is one ring 44 with the cylinder axis sensing unit on it.

Variable diameter cylinder 31 FIG. 2, has a hollow shaft 32. Cylinder 31 consists of rods 33 and spokes 34. Supports 35 and 36, for pivoted spokes, are fixed to the shaft 32. Supports 37 and 38 are movable on the shaft and interconnected within the slotted shaft 32 by means of rod 39, to ensure that 37 and 38 move exactly at the same rate. Each spoke 34 of cylinder 31 is connected by means of pivots 40 at one end to a rod 33 and at the other end to a support, in such a manner that any expansion or contraction ofthe cylinder will keep rods 33 parallel to and equidistant from shaft 32.

As shown by FIG. 2 the lower end of shaft 32 is attached to a float 41 in an oil tank 42. The float 41 and the balancing weight 43 are so designed that the shaft 32 with the cylinder is free from tilting forces when not vertical, so as to adjust itself freely to a position determined by the contraction ofthe cylinder within the duplicated periphery. Cylinder 31 FIG. 2 is expanded by the weight of rods and spokes. Same free adjustment can also be achieved by suspension of the cylinder in oil, so that it floats submerged whereby the cylinder is expanded by spring action.

Cylinder 31 FIG. 2 is expanded by the weight of rods and spokes to its largest diameter as determined by the fully retracted displacement receivers 21. The axis of shaft 32 represents in this case the duplicated datum axis 6 of supports 3 in FIG. 1. Duplication of one periphery by receivers 21 results simultaneously in contraction of cylinder 31. When transmitters 9 FIG. 1 and r'eceivers'2l FIG. 2 stop moving, then cylinder 31 FIG. 2 occupies its correct position in the duplicated periphery. The final position of the axis of shaft 32 determines the center point of the maximum circle in the duplicated periphery. The coordinates of this center point are determined by linear displacement transmitters on ring 44 of the cylinder axis sensing unit. For geometrical reasons the coordinates obtained must be corrected by a constant factor because the log supports, which are shifted correspondingly, are not in the critical cross sections.

The plane through ring 44 FIG. 2 is perpendicular to the duplicated datum axis and the center point of ring 44 is on this axis. Ring 44 FIG. 4 has four displacement transmitters arranged in pairs'45, 46 and 47, 48. The center line determined by one pair 45, 46 is perpendicular to the center line of the other pair 47, 48 and their common point is the center of the ring. These displacement transmitters touch the cylinder only lightly, if compared with the expansion force of the cylinder, and they follow the expansion and contraction. Half of the difference in travelled distance of the displacement transmitters, in one opposing pair, is equal to one coordinate of the cylinder axis with respect to the center point of the ring 44.

Displacement transmitter 46 FIG. 4, moves by means I of an instant stop electric motor 50 till bar 52 of the rack touches the cylinder rod 33. Bar 52 is provided, along the side it approaches rod 33, with a lever 62 as long as the bar. This lever 62 is movable on hinge 63 at one end and at the other end of the bar this lever operates a switch 64 when the lever is pushed flush with bar 52 by cylinder rod 33. Switch 64 reverses the instant stop motor 50 until no contact is made, reverses again till contact is made and so an. Bar 52 with transmitter rack 46 follows the contraction and expansion of the cylinder, with a very small pressure on the cylinder, until a steady state is achieved as a very short clockwise and counter clockwise oscillation of the motor 50. P0- tentiometer 54 provides the position of the bar 52 as a voltage. In the same manner operate all transmitters on ring 44.

Sensing of the cylinder position by bar 52 can also be achieved by operating rack 46 with air pressure. The tip of lever 62 is then the flapper of a conventional air flapper controller valve for moving rack 46.

Centering of the log proper is made by moving supports 3 FIG. 1 vertically and horizontally. Servos 22 FIG. 2 of the duplicating unit are de-energized and stopped. All transmitters 9 FIG. 1 are retracted. Servos l5 and 17 of support 3 are energized and start moving as required by the signals from transmitters on ring 44. On ring 44 FIG. 4 the voltage difference of opposing potentiometers 53 and 54 is proportional to the vertical" coordinate of the cylinder shaft 32 in the plane of ring 44 and the corresponding support 3 is shifted vertically by servo until the potentiometer 16 of this servo shows the same voltage difference. In the same manner the horizontal coordinate is sensed as a voltage difference by the potentiometers of transmitters 47 and 48 FIG. 4 and same support 3 is shifted horizontally by means of servo 17 until potentiometer 18 has the same voltage difference. In a similar manner the other log support is shifted by the other duplicating unit for the other critical cross section. The log is centered. Servos l5 and 17 FIG. 1 are de-energized and stopped and the log is transferred in a conventional manner to the lathe either by means of carriage 10 or it is grabbed by charging arms. Supports 3 are ready to receive a new log. Servos 22 FIG. 2 are energized and all duplicating racks retract, cylinder 31 expands to its largest diameter and the duplicating units are ready for a new operation.

In the above described apparatus, for centering automatically logs with two noncircular critical cross sections, the variable diameter cylinder 31 FIG. 2 can be replaced with a constant or rigid diameter cylinder 71 FIG. 5, so that it is floating freely within the duplicated periphery. After duplication of one periphery in one duplicating unit, each of the n duplicating tips 24 of the receiver racks 21 have their corresponding distance R,, from the datum axis of the duplicating unit. It is now necessary to contract the duplicated periphery proportionally, so that at any time 1 during contraction the distance r,, of a tip n, from the datum axis, is determined by the equation r /R r /R r,,/R,,. This contraction can be achieved by conventional velocity servos or position servos 22, with the potentiometer unit 23 adapted to proceed with the described proportional contraction after duplication. When at least three tips 24 of receiver racks 21 grab the rigid cylinder firmly, so that the switching units in the tips 24 are actuated, then the contraction stops and each tip 24 of the receiver racks 21 has its own final distance p,, from the datum axis and the final contraction factor isf= p,,/R,,. The position of the cylinder axis is now determined as described before by the transmitter racks on ring 44 and the log supports are shifted correspondingly by computer operated servos designed to account for the contraction factor. The advantage of a rigid cylinder is that chords may be omitted between the duplicating tips 24 of the receiver racks 21.

Although there has been shown and described herein a preferred form of the invention, it is to be understood that the invention is not necessarily confined thereto, and that any change in the structure and relative arrangement of components are contemplated as being within the scope of the invention, defined by the claims appended.

I claim:

1. An apparatus for centering peeler logs. on two movable supports, with substantially circular sweep, slight taper and two critical cross sections of irregular shape, comprising in combination:

a sensing unit for sensing the irregular peripheries of two critical cross sections of a log on movable supports for the purpose of duplicating these peripheries,

two duplicating units for duplicating seperately each of said peripheries at a desired ratio,

a cylinder unit in each of said two duplicating units, assigned to shift freely, for the purpose of finding the center point of the maximum circle in said duplicated periphery, whereby these two center points determine the peeling axis,

a center point sensing unit, as part of a periphery duplicating unit, for sensing the coordinates of said center point,

a servo unit, in each of said two movable log supports, for shifting the support in accordance with signals received from the corresponding center point sensing unit.

2. An apparatus for centering peeler logs as defined in claim 1 wherein,

said cylinder unit for finding said center point of the maximum circle comprising, for one periphery, one variable diameter cylinder within the duplicated periphery and said variable diameter cylinder adapted to shift freely into the position of the maximum diameter within said duplicated periphery, so that the position of the cylinder axis determines the coordinates of said center point of the maximum circle,

said coordinates are sensed by said center point sensing unit and said servo units for shifting the supports of the log are operated by said center point sensing units.

3. An apparatus for centering peeler logs as defined in claim 1 wherein,

said two duplicating units for duplicating peripheries are designed to contract said duplicated periphery proportionally and said cylinder unit for finding said center point of the maximum circle comprising, for one periphery, one rigid or constant diameter cylinder adapted to shift freely within said proportionally contracting periphery, until said contracting periphery holds firmly said rigid cylinder in the position of the maximum circle in the contracted periphery, whereby the position of the cylinder axis determines the coordinates of said center point of the maximum circle,

said coordinates are sensed by a center point sensing unit so that,

said servo units for shifting the supports of the log are operated by a computer in combination with said center point sensing units. 

1. An apparatus for centering peeler logs, on two movable supports, with substantially circular sweep, slight taper and two critical cross sections of irregular shape, comprising in combination: a sensing unit for sensing the irregular peripheries of two critical cross sections of a log on movable supports for the purpose of duplicating these peripheries, two duplicating units for duplicating seperately each of said peripheries at a desired ratio, a cylinder unit in each of said two duplicating units, assigned to shift freely, for the purpose of finding the center point of the maximum circle in said duplicated periphery, whereby these two center points determine the peeling axis, a center point sensing unit, as part of a periphery duplicating unit, for sensing the coordinates of said center point, a servo unit, in each of said two movable log supports, for shifting the support in accordance with signals received from the corresponding center point sensing unit.
 2. An apparatus for centering peeler logs as defined in claim 1 wherein, said cylinder unit for finding said center point of the maximum circle comprIsing, for one periphery, one variable diameter cylinder within the duplicated periphery and said variable diameter cylinder adapted to shift freely into the position of the maximum diameter within said duplicated periphery, so that the position of the cylinder axis determines the coordinates of said center point of the maximum circle, said coordinates are sensed by said center point sensing unit and said servo units for shifting the supports of the log are operated by said center point sensing units.
 3. An apparatus for centering peeler logs as defined in claim 1 wherein, said two duplicating units for duplicating peripheries are designed to contract said duplicated periphery proportionally and said cylinder unit for finding said center point of the maximum circle comprising, for one periphery, one rigid or constant diameter cylinder adapted to shift freely within said proportionally contracting periphery, until said contracting periphery holds firmly said rigid cylinder in the position of the maximum circle in the contracted periphery, whereby the position of the cylinder axis determines the coordinates of said center point of the maximum circle, said coordinates are sensed by a center point sensing unit so that, said servo units for shifting the supports of the log are operated by a computer in combination with said center point sensing units. 